Shiagur was a warlord who was also one of the few remaining fertile krogan females following widespread deployment of the genophage circa 700 CE. She used her fertility to amass male followers, who competed with each other for the right to have children with her.
Shiagur's band was not particularly powerful. She was defeated at Canrum by turian forces during the last stages of the Krogan Rebellions. However, vengeful krogan admirers retaliated against her killers when they heard the news, ultimately resulting in thousands of casualties.
Shiagur's bloodline remains a status symbol among present-day krogan, and her direct descendants have the clan brands to prove their lineage. Nakmor Drack is one such descendant, and so is his granddaughter Nakmor Kesh. Grunt, being tank-bred, has some of her genetic legacy along with other krogan deemed "worthy" by his creator Okeer.
Comparing people to Shiagur is considered a mark of honor. The Urdnot Shaman may bestow the compliment upon a female Shepard who understands the krogan better than some of their own kind. Her name is also invoked in a song Mordin Solus may sing for Eve.